ABCC9 and hypertrichotic osteochondrodysplasia Cantu type: However, very rare gain-of-function mutations in ABCC9 under a dominant mode of inheritance cause Cantú syndrome, a disorder characterized by excess hair growth (hypertrichosis) as well as cardiovascular, craniofacial, and skeletal abnormalities and, in some cases, mild speech delays and hoarse voice (65–68).